Every day, we are inundated with ideas that are hackneyed wrongly, but also rightly, about new medical approaches. After the mixtures concocted by grandmother, knowledge promoting a better lifestyle, drugs, surgeries performed remotely and computer-assisted, now that the ailments could now be eradicated by treatments based on living cells.

Cell therapy can be defined as an approach which uses a biological product with a therapeutic effect, which product is produced from the preparation of living human or animal cells. In practice, cell therapy consists of the injection of human cells in order to prevent, treat or alleviate a disease.

It’s about repairing damaged tissue with new cells that will help rebuild them. Isolated or cultured cells can be used to repair damaged tissue, or transformed cells to bring various molecules into tissue. The cell types used in cell therapy are differentiated (mature) and functional cells from an organ, precursor cells from stem cells that have already acquired a certain degree of specialization, and stem cells.

What is a stem cell?

A stem cell is a cell which, when dividing, is capable of giving rise to cells engaged in one or more differentiation pathways or to other stem cells to ensure its own renewal. They are divided into two main categories: embryonic stem cells and adult stem cells. Human embryonic stem cells ignite the imagination because of their immortality and unlimited development potential.

They could be an inexhaustible source of specific cells for basic research and transplant therapies. They have the potential to become any type of cell found in the body (about 200 to 300 different types). They originate from an early embryo. These are the cells that raise ethical issues. However, the cells currently used are immortal lines derived from a limited number of embryonic stem cells. There is therefore no need to use new embryos. Adult stem cells are found in many organs of adult people.

The stem cells found in most tissues have often acquired a certain level of specialization and are therefore limited as to the diversity of tissues that they can generate. In 2007, researchers successfully reprogrammed an adult human skin cell into a stem cell similar to embryonic stem cells1,2. These cells are called induced pluripotent stem cells (iPS cells). It is anticipated that they will replace embryonic cells in research. Many applications are envisaged for these cells; the one with the greatest impact would be an alternative to organ and tissue transplants without presenting the rejection problems.

They could also be useful for generating humanized organs in animal models, for evaluating the metabolism of drugs and their toxicity, for the search for new drugs promoting cell survival and growth, for modeling diseases and cancers and finally , to establish models for studying organ development.

However, there are many challenges that must be overcome to enable the use of these iPS cells. We must not only master the culture and use of these cells, but also induce a good transformation of stem cells and develop an efficient injection technique that allows the survival of implanted cells.

All these conditions combined will make it possible to generate cells which function like adult cells, to generate them in sufficient quantity and to ensure the safety of this approach by reducing the risks of tumor formation or of inappropriate function.